The overall goal of the research program is to understand how the language apparatus, biologically specialized for speaking and listening, becomes adapted to reading and writing. Projects I and II explore the bases of phonology. Project I is concerned with the nature and function of the biological specialization (the speech mode) and with its early development (including cerebral lateralization): the central hypotheses addressed by its experiments are that the basic unit of both perception and production is the gesture, and that the phoneme (the basis of the alphabet) gradually emerges in development from recurrent patters of sound and gesture. Project II principally examines how gestures are organized into syllables, how complex acoustic changes associated with shifts in speaking style arise from relatively simple gestural changes, and how listeners parse the acoustic signal into acoustic constellations the components of which are the consequence of a single gesture. The next three projects study the dependence of reading on the phonological processes of speaking and listening. Project III tests the view that deficits in phonological representation limit the development of phonological awareness and success in learning to read and spell. Project IV draws on both good and poor readers, and on several different writing systems (Serbo-Croatian, English, Hebrew, Chinese) to study the mechanism by which readers relate the written word to its spoken form. Project V seeks to identify the sources of difficulties in reading at the sentence level and to forward the goal of early identification of children likely to develop reading problems; a central hypothesis of this project is that poor readers' comprehension difficulties reflect a bottleneck in phonological processing rather than a lag in the mastery of certain syntactic structures.